Caulking in bathrooms serves two basic functions; first as a sealant against moisture ingression, and secondly, to provide a visually pleasing surface on joints, such as between fixtures and wall or floor finish material. Caulk is no substitute for careful detailing and workmanship, which should solve most moisture and visual problems, but there are always situations where some caulking is required.
You should try to choose your sealants and caulks as carefully as you would your finish materials and fixtures; there are many types available and the proper one can make a big difference in the long run. You’ll see at least a dozen or so different caulk types in the big box home renovation stores, but the three main caulking types used in residential bathrooms are latex, acrylic latex, and silicone caulk.
Latex caulk is good for use when latex based paint is being used for wall finishes. They are water based and make for an easy clean-up, are cheap, and fill holes and cracks well. Also, you can paint over them almost right away after application and they hold the paint easily. For all around use in a bathroom, they should be avoided, since they have relatively low water resistance and flexibility.
More flexibile than straight latex, acrylic latex caulk usually are a little more expensive as well. Justifying the extra expense is easy, however, since these types also hold paint well and can be used as a general bathroom caulk. They also usually come in fungicidal versions which help retard the growth of mildew over the period of time that the fungicide additive takes to leach out of the caulking, normally between 5 to 15 years. Acrylic latex caulk also is available in tints to match common paint colors, which helps with the visual aspect.
Silicone caulk is the most expensive of the three, with durability and flexibility to match. They come in anti-fungal versions, just like the acrylic latex. Some builders like to use them exclusively, but be aware they do have a couple of drawbacks. Perhaps the biggest downside of silicone caulk is their quick set-up time, which means you need to work fast once they are applied; this can lead to sloppy workmanship for the less experienced. They are also difficult to form into a bead that is smooth, requiring a steady hand, plus they are more fussy about having a well prepared surface to adhere to. The other downside is a silicone caulk is not paintable, even if the label says it is. That won’t be a problem if your floors and walls are white, which admittedly is often the case.
Applying caulk might seem like a no-brain job, but there are a few tricks to it you should know about. As noted above, silicone caulk doesn’t like to stick to a dirty surface; this applies to a lesser extent to the other caulk types as well. Both sides of the joint should be cleaned of dust, dirt and grime, whether they are new or old. Any old caulk should be removed from sinks, showers and tubs. Thoroughly clean all surfaces of soap film and dirt, using a water soluble solvent, such as isopropanol, if required.
Caulk needs to be worked with at room temperature. Before using caulk tubes that have been stored outside or in unheated areas, allow them to warm up. A larger joint gap requires a larger opening in the caulk tube’s tip, but a good rule of thumb is the smaller the tip opening the better. The best tip cut is made with a sharp utility knife or pair of heavy shears; you want a nice clean cut. For holding the tip against a joint without inadvertently scrapping out already applied caulk, use a 45 degree angle cut. For a more precise bead placement, use a straight tip cut.
Depending on how much room you have to work and maneuver in, you can either apply the caulk by pushing it out in front of the tip as you drag it, or by pulling it out in back of the tip. The important thing is to get a nice straight line without leaving voids, and while injecting enough caulk into the joint gap to seal it.
To help you get straight lines and aid in cleanup afterwards, carefully lay out template lines with making tape either side of the joint.
Working the Bead
Once you’ve laid down the caulk bead it should immediately be tooled to smooth it out and get rid of any air pockets. This step also improves the caulk’s adhesion. For a professional looking finish, special caulking finisher tools are available, which are sort of a miniature hand trowel, but anything handy works better than your thumb- a plastic knife, wooden popsicle stick or piece of cardboard. Keep a couple of old rags nearby for wiping off any excess caulk from your tools and hands before it dries, especially if working with silicone caulk.
Be sure to remove any making tape prior to the calk starting to skin over, or it may never come off. Consult the manufacturer’s label on the caulk tube for the recommended solvent to use during your cleaning up.